Soldering techniques are often used to avoid difficulties which arise in accurately casting large span dental bridges. To avoid this problem, subunits are cast and assembled by soldering. A detailed understanding of the alloy/solder interface does not exist. There are conflicting reports on alloy/solder epitaxy and on the formation of interfacial phases. This study will correlate the mechanical properties of several dental alloy/solder interfaces with the microstructures observed by cross sectional transmission electron microscopy (XTEM). Five alloys with varying amounts of Au and Pd will be joined using simulated preceramic and postceramic soldering techniques. The alloy/solder strength will be measured using three-point flexural bending. The microstructure will be examined using XTEM. The results of this study should provide a solid experimental basis for the nature of the alloy/solder interface and enable materials scientists to tailor alloy/solder combinations to optimize their important parameters. Phase II of this program will apply the principles learned in Phase I to the development of new alloy/solder combinations. In addition, the techniques developed under Phase I will be extended to other dental materials systems, for example, the ceramic/metal interface.